[Intel-gfx] [PATCH] drm/i915/gt: Fill all the unused space in the GGTT

[Chris Wilson]

Quoting Matthew Auld (2020-03-31 16:07:21)
> On Tue, 31 Mar 2020 at 13:42, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> >
> > When we allocate space in the GGTT we may have to allocate a larger
> > region than will be populated by the object to accommodate fencing. Make
> > sure that this space beyond the end of the buffer points safely into
> > scratch space, in case the HW tries to access it anyway (e.g. fenced
> > access to the last tile row).
> >
> > Reported-by: Imre Deak <imre.deak at intel.com>
> > References: https://gitlab.freedesktop.org/drm/intel/-/issues/1554
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Matthew Auld <matthew.auld at intel.com>
> > Cc: Imre Deak <imre.deak at intel.com>
> > Cc: stable at vger.kernel.org
> 
> Do we not need similar treatment for gen6? It seems to also play
> tricks with the nop clear range, or did we disable gen7 ppgtt in the
> end?

Currently disabled. But yes, if we use nop_clear_range we will need
similar clearing. As this method turned out to be much easier than
expected, I guess we should just do it anyway.
-Chris